Part 1 of 5: What Exactly Is Cancer? Breaking Down the Basics

🔬 1. How Cancer Develops

• Genetic malfunctions are at the heart of cancer. Changes in three main types of genes—proto‑oncogenes, tumor suppressor genes, and DNA repair genes—can trigger uncontrolled cell division and prevent damaged cells from dying properly Verywell HealthCancer.gov.

• Over time, accumulated mutations and genomic instability help cells bypass growth control mechanisms like apoptosis, ignore anti-growth signals and become virtually immortal .

2. What Is a Tumor? Benign vs Malignant

• A tumor (or neoplasm) is an abnormal mass of tissue. Tumors can be benign (non-cancerous) or malignant (cancerous) World Cancer Day+1American Cancer Society+1.

• Benign tumors grow slowly and don’t spread, while malignant tumors can invade nearby tissues and spread to distant body parts (metastasis) Cancer.gov+15Encyclopedia Britannica+15American Cancer Society+15.

3. Not a Single Disease

• There are well over 100 distinct types of cancer, each classified according to the tissue or cell type in which it originates—such as carcinomas (epithelial cells), sarcomas (bone/soft tissue), leukemias and lymphomas (blood/immune) MedlinePlus+2Verywell Health+2kolhapurcancercentre.com+2.

• These cancers differ widely in behavior, treatment, and prognosis. For example, breast cancer that spreads to the lung remains classified as metastatic breast cancer—not lung cancer Verywell Health+1Cancer.gov+1.

4. How Cancer Spreads (Metastasis)

• Cancer may remain localized or metastasize when cells detach from the primary tumor, enter the bloodstream or lymphatic system, and establish new tumors elsewhere Verywell Health+1American Cancer Society+1.

• Once metastatic, cancer is often harder to treat—the majority of cancer‑related deaths occur due to metastasis rather than the original tumor .

5. What Causes Cancer?

• Most cancers arise due to acquired genetic mutations caused by environmental and lifestyle risk factors—such as tobacco use, poor diet, obesity, infections, radiation exposure, and carcinogens Wikipedia+1Wikipedia+1.

• A smaller proportion (5–10%) result from inherited genetic mutations passed down from parents Wikipedia.

6. Key Differences Between Cancer Cells and Normal Cells

Cancer cells share certain hallmark behaviors:

• They divide even when not needed (ignoring growth signals).

• Resist signals that stop growth, and avoid programmed cell death (apoptosis).

• Sustain blood supply (angiogenesis), invade tissue, and metastasize.

• Exhibit genomic instability and evade the immune system WikipediaVerywell Health+1Verywell Health+1.

7. Why Understanding Cancer Matters

Grasping cancer basics helps in:

• Encouraging early detection and regular screening,

• Informing choices around lifestyle risk reduction,

• Supporting progress in targeted treatments and precision oncology based on genetic profiling ,

• Highlighting that some cancers are increasingly viewed as chronic diseases, lasting long-term and managed rather than cured kolhapurcancercentre.com+8Verywell Health+8Verywell Health+8.

✅ Summary Table

References 

American Cancer Society. (n.d.). What Is Cancer? Cancer Basics. Retrieved from American Cancer Society website Macmillan Cancer Support+5Cancer Research UK+5Wikipedia+5Verywell Health+4Verywell Health+4MedlinePlus+4Wikipedia+5Wikipedia+5Wikipedia+5arxiv.org+4American Cancer Society+4Verywell Health+4

National Cancer Institute. (n.d.). What Is Cancer? Understanding Cancer. Retrieved from National Cancer Institute website

Verywell Health. (2023, July 27). Everything to Know About Cancer. Retrieved from Verywell Health Verywell Health+3Verywell Health+3Verywell Health+3

Verywell Health. (n.d.). Cancer Cells vs. Normal Cells. Retrieved from Verywell Health Verywell Health

Wikipedia contributors. (2025, July). The Hallmarks of Cancer. In Wikipedia, The Free Encyclopedia. Retrieved from Wikipedia

Wikipedia contributors. (2025, July). Cancer: Causes and global burden. In Wikipedia, The Free Encyclopedia. Retrieved from Wikipedia

Verywell Health. (2016). Types of Cancer and How They Differ. Retrieved from Verywell Health Verywell Health

Verywell Health. (2020). Is Cancer a Chronic Disease? Retrieved from Verywell Health